Home Forums Hunting & Shooting Ask The Gunwriters 6.5-300 Weatherby Erratic Pressures?

I'm doing some hand loading for the 6.5-300. It is a custom barrel, Krieger in origin.

I've been running some velocity tests using .2 grain increments of US869 and the Barnes 127 LRX. I'm using Brian Pearce's data from Handloader, which calls for a COAL of 3.500". My velocities run about 150-200 fps lower that what he got with his genuine Weatherby rifles.

Across a 2 grain spread I get 3-4 different charges where the velocity decreases significantly (20-40 fps) as charge increases, then starts back up again. This Weatherby brass is not new, has been annealed and full-length sized and expanded in a separate step from the sizing.

Is this common in such overbore cartridges as this one? The 300 Weatherby and 257 Weatherby do not show this phenomenon, at least for me.

I’m not a gun writer but am a 6.5-300 Wby owner and shooter.

I’ve killed two animals with mine. I as well used the Handloader data and just went with Max loads because they shoot great in my rifle and I didn’t want to burn my barrel doing load development. I get MOA or a tad sub with 94 gr. of US869 with Rem 91/2 primers and the 127 LRX or the 129 Hornady Interbond. I killed a huge black bear with the LRX and a small buck with the interbonds.

I shoot a factory Weatherby Vanguard Wilderness. The trouble I run into is a fouled barrel changes everything and it fouls very easily. I have to decopperize every 21 (the 1st shot is a fouler) shots or things....get interesting... if a cartridge and chambering were a race car this one would be a top fuel dragster and is super high maintenance. I use patchout from wipeout and make sure I apply some patience as well.

Make sure you keep your barrel clean and measure each powder charge. I know 869 measures really easy but this cartridge is very touchy.

I love my 6.5-300 but it isn’t for the faint of heart and I’ll never recommend it to people who like boring guns.

I also think this is one cartridge that could use weatherby’s free bore, so hopefully your custom has some.

Good luck,

Todd

Rodell,

You don't mention the barrel length of the Krieger barrel, whether the chamber is standard, or what primer you're using. Those might affect what you're seeing--along with the chronograph.

I have handloadered for the 6.5-300 quite a bit, partly due to doing an article on it for the 2018 Hodgdon Annual Manual. Even before I started trying their data, Hodgdon's head tech guy, Ron Reiber, used exactly the same word Justahunter did to describe it: "touchy." This tends to be true of any cartridge with any "overbore" rifle round, but the 6.5-300 is far more overbore than either the .257 or .300 Weatherby.

Part of the problem is that there are relatively few handloading powders slow enough to really perk in such rounds. In my factory rifle (a Mark V Ultra Lightweight) US869 turned out to work best with bullets in the 140-grain class (just as it does in the 26 Nosler) but that doesn't mean it won't be touchy.

Fouling, as Justahunter noted, can also be a problem, even with a Krieger barrel.

I’d think that WC-872 would work well in the 6.5-300 Weatherby. I have 3 8 pound jugs that I bought for my 300 Rum. and it is really too slow even with 200 grain bullet. May work well with 240 SMK

Agree on finding slow enough powder. The "touchy" stuff goes away with the 26 Nos and I would think the 6.5-300 Wby as they aren't that far apart.

869 works great, as does 872. Same loads, same bullets, same velocity and trajectory. I know you can't get too far out in the weeds with surplus or non std. powders, but 872 can be had a lot cheaper. So, while it's available, I use it along with 869.

Jeff Bartlett sells it, $55/8#s. http://gibrass.com/gunpowder.html

DF

My chronograph is a labradar, and I have no reason to doubt it. I get consistent readings whenever I use it. I suppose it could be inaccurate, but I don't think inconsistent. My chosen primer is a CCI250 - I use CCI for everything as I have quite a few on hand. Barrel length is 26" with a 1:8" twist and has the "standard" freebore.

It does foul badly - I clean it after every session. I DBC'ed the barrel when I got it, so I don't know how it would have been without it. It usually takes a few soaks with Acclerator/Wipe-Out to get it clean. No biggie, as this is not a "plinking" round for me. I have shot about 200 rounds through it testing various scenarios.

I've occasionally seen dips when doing velocity ladders, but none like this one. The flat spot (if you can call it that) is pretty small. While I understand "slow" barrels, 150-200 fps seems like a lot.

Does the 26 Nosler exhibit any of this "touchiness"? Hill Country Rifles thought a 1-8 twist is on the fast side for the Weatherby but they gave up on it at least for now. When the 264 Winchester came out there were similar remarks made but now we have several ideal powders for it and you don't see the original complaints anymore. Do any of the 50 Caliber powders work well in the Weatherby? This might be one of those cartridges that could benefit from coated bullets.

Rodell,

Thanks for the info. No doubt your Labradar is correct, but a bunch of handloaders still use Shooting Chronys! I also used CCI 250's in my factory 6.5-300 and didn't see any of the velocity dips you did, whether with US869 or any other powder, and was very close to matching both Brian's and Hodgdon's listed velocities. Since yours has a factory-spec chambers, I would guess the barrel's interior dimensions are somewhat "looser" in dimensions. I haven't encountered that with Kriegers, but that's the logical explanation.

Thanks, MD. The reamer was a SAAMI spec reamer and the cases measure out ok. If the bore were loose that could certainly account for the drop in velocity. I guess the only solution is to build another one! Or, I could catch one of the bullets and look for gas checking! Anyone got a net?

Here is the velocity ladder. This is US869, 3.500", 127 LRX. Note how the velocity goes up and down and up again.

Rodell,

I'm a little slower than the Hogdon data. I'm 3455 FPS (over a magnetospeed) with 94 of US 869 with the 127 LRX. I haven't measured the 129 interbond and doubt I will. FYI..

It sounds like you very experienced and that you clean after every session. Just sitting here, I can't help but think your problems revolve around fouling. I would advise you clean more.... If I were personally having that problem, I would clean after every ladder, shoot a fouler, let my barrel cool, then shoot the next test group keeping my barrel very cool. Or start with a 94 gr. charge on a clean barrel and see where you land. Past that, I have no further advise...

Good luck,

Todd

i did not read all the posts but remember Roy Weatherby when he built and chambered his rifles his bullets were seated not to touch the end of the chamber or lance,his rifles and frame was to jump his bullets into the end of chamber. are you seating your bullets to far out ? Mule Deer can explain it much better than any of us how and why.

My 26 Nosler has a 26" SS Shilen barrel. I DBC treated it before I started shooting it. Fouling isn't a problem. Wipe Out takes care of it with a couple of soaks.

My favorite bullets so far have been the 120 TTSX and 120 E-Tip, both running around 3,450 fps with sub MOA accuracy at 400 yds., actually between 2-3" at 400.

Next best is the 127 LRX, which shoots around MOA. My hunting buddy loves the 140 NAB, which shoots slower, around 3,250 or so. I can't tell any difference in terminal performance on WT's and hogs between those and the faster monos. And the 140 NAB is about as accurate, at least MOA.

An interesting powder, one I've not worked up with any details but shows promise is Vv n-570. It's faster burning than 869 or 872, but is high energy and may out perform those two. It could be harder on the throats because of high energy, probably burns hotter.

My Nos has around 500 rounds so far, showing some early throat erosion thru the Hawkeye, accuracy not affected. I think it'll do another 500, but I guess time will tell.

DF

My 26 Nosler in on an old 7RM BDL 700. I set it up with a 3.6" RUM mag box and follower. I tried loading it long, but best accuracy and performance seemed to be when loaded around factory 3.4" COAL. That give it some extra jump or "free bore" so to speak. Monos like to jump, anyway, so it seems to work out.

DF

Rodell,

I wouldn't worry at all about that much velocity variation when chronographing single rounds with only .2 grain variation in the powder charges. Thought you were talking about the averages of at least three rounds, with more of a change in the powder charge between 'em.

But yeah, you are getting pretty low velocities. What overall length did you load them to?

94 gr. 869 with a 127 LRX is a pretty healthy charge to be getting only 3,300+ fps.

Maybe we're talking about a "slow" barrel. I guess slightly oversize could be an explanation. With such a high performance round, it probably wouldn't take that much variation to make a difference. A pressure reading would be interesting. With those velocity readings, pressure may be lower than one would think. So, do you push the charge until you see the velocity that you expect...??

DF

John, This ladder was loaded to 3.500", from the Pearce data. Oddly enough, it doesn't change much when loaded to 3.575", another spot I've found where I get some good results.

I have a few loads that shoot ok, but have been trying a velocity ladder to dial-in better. That usually works for me but the flat spots are few and narrow. I usually find a flat spot that is .6 grain wide - no such luck here. The middle of the flat spot usually results in the best load for that bullet.

When I do groups I always capture the Es and use that to see how I'm doing for consistency in the brass/powder department. I always weigh every charge and, in this case, anneal after every firing.

If I seated them to touch the lands they'd fall out of the case! Thank you Mr. Weatherby.

The rounds in this discussion are set to 3.500", and the max COAL is 3.600". The LRX, being long due to its construction, protrudes greatly into the powder space at any depth.

Try some at 3.6” COAL may help with consistency. .2 of a grain is too small of difference in my opinion for a case that large.

What snout? Maybe I missed it. I went broughton, gtg....

Rodell,

"Protruding into the powder space" is far less serious than many handloaders believe. A bunch of cartridges suffer from that affliction and still work fine, in terms of both accuracy and velocity.

Partly this is due to the fact that any reduction in powder capacity only results in about 1/4 as much reduction in potential velocity, given equal pressures. For instance, seating a 6.5mm bullet .1 inch deeper in a case holding 90 grains of powder reduces "capacity" about 1.6 grains, or 1.8%. This means potential velocity will be reduced around 15 fps in a load capable of 3500 fps.

This reduction also works exactly the same way whether the base of the bullet ends up below the case neck, or inside the neck.